2 5 8 



PHYSIOLOGICAL CHEMISTRY. 



FIG. 83. 



except in cases where the urine has undergone this change within 

 the organism and is voided in the decomposed state. Ammonia- 

 cal fermentation is ordinarily due to cystitis or occurs as the result 

 of infection in the process of catheterization. A microscopical ex- 

 amination of such urine (Fig. 81, p. 257) shows the presence of 

 ammonium magnesium phosphate crystals, amorphous phosphates 

 and not infrequently ammonium urate. 



Occasionally a urine which possesses a normal acidity when 

 voided, upon standing instead of undergoing am- 

 moniacal fermentation as above described will be- 

 come still more strongly acid in reaction. Such a 

 phenomenon is termed acid fermentation. Accom- 

 panying this increased acidity there is ordinarily a 

 deepening of the tint of the urinary color. Such 

 urines may contain acid urates, uric acid, fungi and 

 calcium oxalate (Fig. 82, p. 257). On standing for 

 a sufficiently long time any urine which exhibits 

 acid fermentation w 7 ill ultimately change in reaction, 

 due tp the inception of alkaline fermentation, and 

 will show, the microscopical deposits characteristic 

 of such a urine. 



Specific Gravity. The specific gravity of the 

 urine of normal individuals varies ordinarily be- 

 tween 1.015 and 1.025. This value is subject to 

 wide fluctuations under various conditions. For in- 

 stance following copious water- or beer-drinking the 

 specific gravity may fall to 1.003 or lower, whereas 

 in cases of excessive perspiration it may rise as 

 high as 1.040 or even higher. Where a very accu- 

 rate determination of the specific gravity is desired 

 use is commonly made of the pyknometer or of the 

 Westphal hydrostatic balance. These instruments, 

 however, are not suited for clinical use. The 

 clinical method of determining the specific gravity is by means 

 of a urino meter (Fig. 83, p. 258) . This affords a very rapid method 

 and at the same time is sufficiently accurate for clinical purposes. 

 The urinometer is always calibrated for use at a specific temperature 

 and the observations made at any other temperature must be sub- 

 jected to a certain correction to obtain the true specific gravity. In 

 making this correction one unit of the last order is added to the 

 observed specific gravity for every three degrees above the normal 



As* 



URINOMETER AND 

 CYLINDER. 





